We've eaten at all three and here's how I would rank them:
1. Chefs de France - Great menu selection, food and service was fabulous. We are going here again this year because there were so many other things on the menu we wanted to try.
2. Coral Reef - Long wait for table even with ADR, really loud. Food was good, service ok, a bit rushed. It's worth it to do at least once, but I don't thing we'll be going back any time soon.
3. San Angel Inn - Awesome atmosphere, really peaceful and a nice cool break from the hot weather! Food was so-so, service was slow even though we went at an off time. I do have to admit that even though the food wasn't memorable, I'd be tempted to go here again someday just for the atmosphere.
These are just opinions, your mileage may vary. Look at the menus online and see what appeals to you most, I think every Epcot restaurant is worth trying!